In numerous applications in the electrical art, the electrical circuits needed have been fabricated using various methods that have become known as microcircuits. Although some of these circuits can be very large in size, the internal conductors and components generally are very small and fragile; and thus their manufacturing process must be continually monitored and controlled to prevent defective circuits.
One common monitoring method is to test the product during and after manufacturing. The usual method of testing such a product is to mechanically probe the internal circuitry, using various shaped metallic probes. Although fixed position probes have been used, the increasing density and the larger number of different circuit codes which a manufacturer must produce has required manufacturers to use movable probes, positioned by computer controlled robotic means.
In either case, unless great care is taken, the act of mechanically probing the circuit often damages the circuit under test. The damage during such probing occurs because of one or more factors, e.g., the shape of the probe, impact force of the probe when contacting the circuit, the subsequent static force applied to the circuit, and mechanical lateral motion of the probe in contact with the circuit under test.
Also, because of the need to test large numbers of circuits as fast as possible, the speed required to lower and raise the probe to and from the circuit, and the resulting momentum imparted to the probing assembly often creates high impact forces, over-travel, and a damaging lateral movement of the probe on the circuit.
Probes that make contact to the circuit at an angle that is not perpendicular to the surface of the circuit cause damage, resulting from the normal rubbing or wiping action caused by the bending of the extended flexible section of the probe body during probe flexing.
As a result, the probing of the circuits as a method of reducing manufacturing defects or the testing of completed circuits can actually cause defects.